The split-circulation assist device (SCAD) divides the systemic circulation in two by descending aortic occlusion ; the upper part is maintained by the heart assisted by intraaortic balloon pumping (IABP), and the lower is by percutaneous cardiopulmonary support (PCPS). 1) SCAD made easier the assessment of cardiac performance by excluding the variable 'bypass flow rate' of PCPS from the upper circulation. 2) SCAD increased the IABP effects. 3) SCAD set different arterial pressure in the upper circulation from that in the lower one, for example, by maintaining a minimum possible aortic pressure while keeping the maximum possible renal artery pressure in patients with renal dysfunction. A SCAD catheter made for animal experiment had a 12-cc pumping balloon and two 4-cc occlusion balloons, which were inflated alternately, thereby preventing the continuous ischemia to Adamkiewicz arteries. The catheter shaft was mad smaller at the balloon segment (7 Fr) whereas the other segment was 1arger (8 Fr) in order to prevent the balloon segment from being bulky when the balloons were wrapped. This structure also maintained high performance of IABP.A con troller for the two balloons was developed and programmed to split the circulation continuously by setting an overlap period (OP) when the inflation of both balloons were overlapped. The OP and the phase from one inflation to the next were set at ranges of 1.5 to 7.5 and 20 to 60 sec, respectively. An inflation pressure of 200 mmHg ensured the continuous split-circulation against mean blood pressure of 100 mmHg even when the OP was set at 1.5 sec. The SCAD catheter and the controller were tested in five dogs. The balloon pumping and the continuous split-circulation were successful in all the cases. After 2 to 3 hr pumping, no obvious injury was observed at the sites of balloon pumping an occlusion.